Quantification of midostaurin in plasma and serum by stable isotope dilution liquid chromatography-tandem mass spectrometry: Application to a cohort of patients with acute myeloid leukemia.

OBJECTIVES: Midostaurin is an oral multitargeted tyrosine kinase inhibitor for the treatment of acute myeloid leukemia (AML). Therapeutic drug monitoring of midostaurin may support its safe use when suspecting toxicity or combined with strong CYP3A4 inhibitors. METHODS: A stable isotope dilution liquid chromatography-tandem mass spectrometry method was developed and validated for the determination and quantification of midostaurin in human plasma and serum. Midostaurin serum concentrations were analyzed in 12 patients with FMS-like tyrosine kinase 3 (FLT3)-mutated AML during induction chemotherapy with cytarabine, daunorubicin, and midostaurin. Posaconazole was used as prophylaxis of invasive fungal infections. RESULTS: Linear quantification of midostaurin was demonstrated across a concentration range of 0.01-8.00 mg/L. Inter- and intraday imprecisions of the proposed method were well within ±10%. Venous blood samples were taken in nine and three patients in the first and second cycle of induction chemotherapy. Median (range) midostaurin serum concentration was 7.9 mg/L (1.5-26.1 mg/L) as determined in 37 independent serum specimens. CONCLUSION: In a real-life cohort of AML patients, interindividual variability in midostaurin serum concentrations was high, highlighting issues concerning optimal drug dosing in AML patients. A personalized dosage approach may maximize the safety of midostaurin. Prospective studies and standardization of analytical methods to support such an approach are needed.

Drug-drug interactions in Neonatal Intensive Care Units: how to overcome a challenge.

INTRODUCTION: Critically ill patients in neonatal intensive-care units (NICU) are exposed to a large number of drugs. Clinical trials for safety, dosing and efficacy are lacking although age-dependent alterations of pharmacokinetics (PK), drug-drug-interactions (DDIs), as well as intravenous admixture incompatibilities (IAI) may impact drug efficacy and trigger side-effects in this vulnerable population. Consequently, implementation of a routinely used DDIs checking regimen may help guide in decision making and will assist clinicians to avoid serious and preventable events. Therefore, the goal of the present work is to identify and assess the risk of relevant DDIs of drugs commonly used in the NICU. EVIDENCE ACQUISITION: A literature review study was performed to identify and further assess the risk of relevant DDIs of 48 drugs frequently used in the tertiary care NICU of the University Hospital of Cologne. DDIs were categorized into five different classes according to their severity (contraindicated, minor, moderate, and major DDI, IAI), based on the classification used in the Micromedex database. In the database a major interaction is defined as any interaction that can be life threatening and/or demands medical intervention to avoid severe adverse effects. Moderate interactions can lead to a degradation of the patient's status and demand an adjustment in the therapy, and minor interactions only have a limited clinical effect. All identified DDIs in the present study are presented as a Visual Interaction Triangle (VIT) and recommendations on the management of clinically significant DDIs are provided. EVIDENCE SYNTHESIS: According to the classification used in the Micromedex database: a total of 160 (13.2%) possible interactions (DDI, IAI) were found. Fifty-five (4.9%) cases were categorized as serious interactions (DDI-major), 48 (4.2%) were less severe (DDI-moderate/minor) and in 52 (4.6%) cases an intravenous admixture drug interaction was found. Five (0.4%) drug-combinations were contraindicated. CONCLUSIONS: In this web-based study, a total of 160 DDIs were identified. Although only 4.9% were classified as clinically relevant, practitioners can use the presented VIT as a unique clinical reference to avoid possible predictable adverse effects and to uncover possible drug-interaction potential.

Quantification of direct-acting oral anticoagulants: Application of a clinically validated liquid chromatography-tandem mass spectrometry method to forensic cases.

In certain forensic cases, a quantification of direct-acting oral anticoagulants (DOACs) can be necessary. We evaluate the applicability of a previously described liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodology for the determination of DOACs in plasma to postmortem specimen. Postmortem internal quality control (PIQC) samples were prepared in pooled blank postmortem heart blood, femoral blood, cerebrospinal fluid (CSF), and urine as well in plasma. To examine the application of the clinical method to forensic cases, the main validation parameters were reinvestigated using PIQC samples. Postmortem samples of 12 forensic cases with evidence of previous rivaroxaban intake and unknown bleeding disorders were analyzed. Interday variability remained within the acceptance criterion of ±15%. Matrix effects were comparable in blank plasma and postmortem matrix extracts. After 4 weeks of storage in the refrigerator, no relevant decrease of DOACs was evident. After 96 h of storage at room temperature, a slight decrease in edoxaban concentration was observed in CSF and urine, while plasma edoxaban decreased by about 50%. Median (range) rivaroxaban concentrations determined in specimen of forensic cases were as follows: heart blood (n = 6), 17.2 ng/ml (

Pharmacodynamic Monitoring of Mycophenolic Acid Therapy: Improved Liquid Chromatography-Tandem Mass Spectrometry Method for Measuring Inosin-5'-Monophosphate Dehydrogenase Activity.

BACKGROUND: Mycophenolic acid (MPA), a powerful inhibitor of lymphocyte proliferation, is widely used in transplantation medicine and as a glucocorticoid-sparing agent in rheumatic and inflammatory diseases. As inosine-5'-monophosphate dehydrogenase (IMPDH), the target enzyme of MPA, shows high interindividual variability in its basal activity, the assessment of IMPDH activity in addition to pharmacokinetic monitoring has emerged as a strategy to individualize MPA pharmacotherapy. METHODS: A liquid chromatography-tandem mass spectrometry method was developed to measure IMPDH activity in peripheral blood mononuclear cells from lithium-heparinized blood. Stable isotope-labeled analogs of analytes were used as internal standards for the quantitative analyses of xanthosine-5'-monophosphate (XMP) and adenosine-5'-monophosphate (AMP). IMPDH activity was expressed as enzymatic production of XMP per time normalized to the AMP concentration. Validation and evaluation of the new method were performed by using blood samples from healthy volunteers (n = 10). RESULTS: Linearity was demonstrated over the concentration ranges of 0.25-80 µM for XMP and 4-80 µM for AMP (R > 0.99). Between-day and within-day assay precisions and accuracies were within the acceptance criterion of ±15%. Matrix effects were fully compensated by the coelution of internal standards. Specific and linear XMP production (R > 0.99) and the inhibition of IMPDH activity by MPA at clinically relevant doses were demonstrated. CONCLUSIONS: In this study, a liquid chromatography-tandem mass spectrometry method to measure IMPDH activity was established and fully evaluated for matrix and ion suppression effects. The method enabled precise quantification of IMPDH activity for the improvement of pharmacokinetic/pharmacodynamic therapeutic drug monitoring approaches to optimize immunosuppressive treatment with MPA.

Cost-effectiveness of TLC-sucrose octasulfate versus control dressings in the treatment of diabetic foot ulcers.

OBJECTIVE: Diabetes is one of the most widespread diseases in Germany. Common complications are diabetic foot ulcers (DFU), which are associated with a cost-intensive treatment and serious adverse events, such as infections, amputations. This cost-effectiveness analysis compares two treatment options for patients with DFU: a TLC-NOSF dressing versus a neutral dressing, assessed through a European double-blind randomised controlled trial (RCT), Explorer. METHODS: The evaluation of the clinical outcomes was associated to direct costs (costs for dressings, nursing time, hospitalisation etc.) of both dressings, from the perspective of the statutory health insurance in Germany. Due to the long mean healing time of a DFU, the observation period was extended from 20 to 100 weeks in a Markov model. RESULTS: After 20 weeks, and with complete closure as a primary endpoint, the model revealed direct treatment costs for DFU of €2,864.21 when treated with a TLC-NOSF dressing compared with €2,958.69 with the neutral control dressing (cost-effectiveness: €6,017.25 versus €9,928.49). In the Markov model (100 weeks) the costs for the TLC-NOSF dressing were €5,882.87 compared with €8,449.39 with the neutral dressing (cost-effectiveness: €6,277.58 versus €10,375.56). The robustness of results was underlined by several sensitivity analyses for varying assumptions. The frequency of weekly dressing changes had the most significant influence in terms of parameter uncertainty. CONCLUSION: Overall, the treatment of DFU with a TLC-NOSF dressing is supported from a health economic perspective, because both the treatment costs and the cost-effectiveness were superior compared with the neutral wound dressing.

Reliable and Easy-To-Use Liquid Chromatography-Tandem Mass Spectrometry Assay for Quantification of Olorofim (F901318), a Novel Antifungal Drug, in Human Plasma and Serum.

A fast and easy-to-use liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination and quantification of a novel antifungal drug, olorofim (F901318), a member of the novel class of orotomides, in human plasma and serum was developed and validated. Sample preparation was based on protein precipitation with acetonitrile and subsequent centrifugation. An isotope-labeled analogue of F901318 was employed as an internal standard. Chromatographic separation was achieved using a 50-mm by 2.1-mm, 1.9-µm, polar Hypersil Gold C18 column and isocratic mobile phase consisting of 0.1% formic acid-acetonitrile (60%-40%, vol/vol) at a flow rate of 330 µl/min. The analyte was detected using a triple-stage quadrupole mass spectrometer operated in selected reaction monitoring (SRM) mode with positive heated electrospray ionization (HESI+) within a single runtime of 2.00 min. The present LC-MS/MS method was validated according to the international guidelines of the International Conference on Harmonisation (ICH) and the U.S. Food and Drug Administration (FDA). Linearity of F901318 concentration ranges was verified by the Mandel test. The calibration curve was tested linear across the range and fitted using least-squares regression with a weighting factor of the reciprocal concentration. The limit of detection was 0.0011 mg/liter, and the lower limit of quantitation was 0.0033 mg/liter. Intraday and interday precisions ranged from 1.17% to 3.23% for F901318, and intraday and interday accuracies (percent bias) ranged from 0.75% to 5.01%. In conclusion, a method was established for the rapid quantitation of F901318 concentrations in serum and plasma samples in patient trials, and it optimizes therapeutic drug monitoring in applying an easy-to-use single method.